Hollow profiles are used in many applications where strength is required. For example hollow profiles are used in automobiles, trucks and busses as part of the supporting sub frame, pillars and roof structures. Similarly hollow profiles are used in aircraft and shipping and in the construction industry.
It is also known to reinforce hollow profiles with ribbed structures positioned within the profile and in this way additional strength may be provided to the profile without requiring a dramatic increase in the weight of the profile. It has also been proposed that a heat foamable adhesive material may be provided on a reinforcing structure so that the structure may be inserted into the hollow profile and thereafter foamed by heating so that the material expands and bonds the structure to the under surface of the hollow profile. Furthermore it has been proposed that in automobile manufacturer the heat foamable material be such that it will foam at the temperatures experienced in the oven used to bake the anticorrosion coating typically applied to the metal frame of an automobile sometimes known as the “e-coat” process.
The previous proposals have however related to I beam structures such as those illustrated in PCT Publication WO 9743501 or to tubular hollow profiles such as those illustrated in EP 1265765. In these structures the foamable material is provided over a substantial surface area and which requires large amounts of foamable material in order to achieve a satisfactory bond between the reinforcing structure and the hollow profile. In addition these proposals rely upon the foam, once formed, to provide a contribution to the reinforcing effect.
Another form of reinforcement has been proposed in for example European Patent Applications 0370342 and 0995668 and French 2817943. In these proposals steel sections are overmoulded with polymeric ribbed structures and in many instances the polymeric material is nylon. However although nylon is a preferred polymeric material it will not adhere to steel sections and it is therefore necessary to provide mechanical interlocking between the overmoulded ribbed section and the steel such as the provision of holes or ribs in the steel around which the molten polymer can be injected in its molten state so that it will solidify to form a mechanical bond between the ribbed structure and the metal. This requires a complicated metal structure and the use of more polymer than is required for the reinforcing ribbed structure.
Vehicles require reinforcement for a variety of reasons. For example, vehicles can be reinforced against impact such as in a crash. However, even in crash reinforcement a variety of types of reinforcement may be required, different reinforcement being required for front impact, side impact, rear impact and rollover crash. In addition vehicles need to be reinforced against regular noise, vibration and harshness during regular working (sometimes known as NVH). The reinforcement needs to provide a combination of energy absorbing and energy dissipating functions depending upon the nature of the reinforcement required and the position in the vehicle that is to be reinforced and different structures are used to provide different types of reinforcement.
Vehicle body shells are generally assembled from hollow profiles generally metal structures consisting of longitudinal supporting structures, sometimes known as longits or rails. Transverse supporting structures of which there are usually at least three, front, middle and rear. Pillars for the doors and supporting the roof extending upwards from the longitudinal structures and frequently there are three pairs of pillars the A pillars at the front of the vehicle which pass upwards behind the engine compartment and contain the windscreen in its upper portion, the B pillars behind the front doors of the vehicle and the C pillars at the rear of the vehicle. Larger vehicles can have a larger number of pairs of pillars. Reinforcement is also provided within doors and also to support grooves at the front and the back of the vehicle.
Different areas of the vehicle require reinforcement for different reasons. For example the front of the longitudinal section and the A pillars require reinforcement against front crash but they also require stabilisation to remove vibration and hardness of driving. The centre of the longitudinal structures and the B pillars require reinforcement against side crash but also against front crash and to remove vibration and hardness during driving. The rear of the vehicle and the C pillars require reinforcement against rear crash and also against vibration and hardness during driving. The A, B and C pillars all require strengthening against roll over crash particularly at the top of the pillars. Overmoulded ribbed structures have been proposed for door reinforcement and roof supports.
It is important that the provision of the reinforcement be achieved within the normal vehicle assembly operations. One important operation in vehicle manufacture is the provision of an anti corrosion coating on the internal surfaces of the metal structures and this is often accomplished by what is know as the electrocoat (or e coat) process. In this process the assembled metal frame of the vehicle passes through a large bath of anti corrosion fluid which is deposited electrolytically on the metal and the coating formed is then cured by passing the coated metal structure through an oven where it is dried and hardened. Techniques have been developed whereby a reinforcing part comprising a carrier material which provides reinforcement carrying a heat activated adhesive foamable material is placed within the metal structure and the metal structure is subject to the e-coat process. The foamable material is designed so that it will foam and develop adhesive properties under the conditions employed for the drying and/or hardening of the anti corrosion coating. In this way the foamable material can be foamed after deposition of the anticorrosion coating during the drying and curing of the coating. The foamed material therefore serves the dual function of adhering the carrier to the inner surface of the tubular structure so that the carrier can provide a reinforcing effect and also contributing to the reinforcement.